In a typical Universal Mobile Telecommunications System (UMTS)/High Speed Packet Access (HSPA) system, a User Equipment (UE) with a Radio Resource Control (RRC) Connection can be in one of the following states: Cell Dedicated Channel (CELL_DCH), Cell Forward Access Channel (CELL_FACH), Cell Paging Channel (CELL_PCH), or UMTS Terrestrial Radio Access Network (UTRAN) Registration Area Paging Channel (URA_PCH). A UE with data traffic is put into the CELL_DCH state or the CELL_FACH state, such that the UE is able to transmit and receive user data. A UE with low burst traffic activity typically is put into the CELL_FACH state.
The Third Generation Partnership Project (3GPP) develops releases of UMTS-based systems, such as the UMTS/HSPA system. In 3GPP Release 7, a new state (denoted as Enhanced CELL_FACH) was introduced into the UMTS/HSPA system in order to allow a UE to receive High Speed Downlink Packet Access (HSDPA) packets, thereby enabling the UE to receive large bursts of downlink traffic. In 3GPP Release 8, another new state (denoted as Enhanced Uplink CELL_FACH) was introduced into the UMTS/HSPA system in order to allow a UE to send High Speed Uplink Packet Access (HSUPA) packets, thereby enabling the UE to send large bursts of uplink traffic. The Enhanced Uplink CELL_FACH state is a superset of the Enhanced CELL_FACH state, meaning that the HSUPA in CELL_FACH requires the HSDPA in CELL_FACH. The bursty nature of smartphone traffic is well suited for the Enhanced Uplink CELL_FACH state, because the Enhanced Uplink CELL_FACH state uses resources (namely, HSDPA and HSUPA resources) more efficiently than the CELL_DCH state. As the number of smartphone devices is expected to increase significantly in the future, it also is expected that increasing numbers of UEs will reside in the Enhanced Uplink CELL_FACH state.
Disadvantageously, however, while the introduction of such new states has certain advantages, the introduction of such states also may cause degradations in aggregated cell throughput capacity and signaling reliability.